1. Field of the Invention
The present invention relates to a latent image carrier unit including at least a latent image carrier which is removable from a body of an image forming apparatus and the image forming apparatus using the same.
2. Description of the Related Art
Conventionally, there is known an image forming apparatus of this type as disclosed in Patent Document 1. The image forming apparatus includes a photoconductor unit as a latent image carrier unit removable from a body of the image forming apparatus. This photoconductor unit holds a photoconductor as a latent image carrier, a charging roller as a member, and a cleaning member disposed in a peripheral portion of the photoconductor, all enclosed in a common casing as a single unit.
A first positioning protrusion and a second positioning protrusion are disposed on both surfaces of the casing of the photoconductor unit. On the other hand, a first slit in engagement with the first positioning protrusion and a second slit in engagement with the second positioning protrusion are formed on two side plates installed upright in the body of the image forming apparatus to face each other with a predetermined distance. On one side of the photoconductor unit, while the first positioning protrusion of the photoconductor unit is engaged with the first slit on the side plate of a body of the image forming apparatus, the photoconductor unit is inserted in an installation and removal direction of the unit as a longitudinal direction of the first slit to be installed on the body of the image forming apparatus. In this case, when the first positioning protrusion of the photoconductor unit is slidably moved within the first slit and is brought into abutment with an end of the first slit, the photoconductor unit is positioned in the installation and removal direction inside the body of the image forming apparatus.
Further, the second positioning protrusion of the photoconductor unit is engaged with the second slit on the side plate of the body of the image forming apparatus immediately before the positioning. In accordance with this, the photoconductor unit is positioned at a portion different from the first positioning protrusion. Moreover, on the other side of the photoconductor unit, the first positioning protrusion of the photoconductor unit is brought into abutment with an end of the first slit on another side of the body of the image forming apparatus in the same manner. Then, the second positioning protrusion of the photoconductor unit is engaged with the second slit on the other side in the body of the image forming apparatus.
In accordance with such a structure, the photoconductor unit is positioned at the first positioning protrusion and the second positioning protrusion having positions differing from each other on both sides inside the body of the image forming apparatus, so that it is possible to position the entire photoconductor unit and correct posture thereof.
Patent Document 1: Japanese Laid-Open Patent Application No. 2002-108173
However, in such a structure, downsizing of the body of the image forming apparatus becomes difficult due to the following reasons. Specifically, it is desirable that the photoconductor unit have a flat shape when the image forming apparatus is downsized. In particular, in what is called a tandem type color image forming apparatus employing plural photoconductor units each forming a toner image of different color, flattening of each unit is an important factor in downsizing the body of the image forming apparatus because it is possible to have a compact installation space for the photoconductor units by arranging the flat photoconductor units in a thickness direction thereof. In such a layout, each photoconductor unit is designed to slide in the unit thickness direction inside the body of the image forming apparatus in order to be installed or removed from the body of the image forming apparatus. In this structure, even when only a third unit from a front side is desired to be replaced, for example, a first unit and a second unit from the front side must be first pulled out from the body of the image forming apparatus. In accordance with this, a structure allowing each photoconductor unit to be separately installed and removed is employed. On the other hand, the first positioning protrusion and the second positioning protrusion formed on both sides of the photoconductor unit are required to have a certain size because of the necessity for maintaining a desired positioning accuracy and for providing strength capable of withstanding an impact upon installation of the photoconductor unit. In order to engage the relatively large first positioning protrusion and the second positioning protrusion with separate slits on both sides of the photoconductor unit slidably moving in a direction substantially orthogonal to the thickness direction of the photoconductor unit, these protrusions must be arranged in the thickness direction on both sides of the photoconductor unit. Thus, reduction of the thickness of the photoconductor unit or flattening of the photoconductor unit is difficult.